does it matter?
How many people would you unjustly exterminate in order to appease your Fuehrer?
And why do you think a dissenter would stand alone in refusal of unacceptable orders? Is it perhaps due to the fact that most of them actually agreed with the orders? It's not like they were a hopeless disarmed populace of malnourished weaklings.
Also: what do you think happens to people who tell police "no sir" in Nazi America?
Yes it matters. In nazi germany they wouldn't just kill you, but your family also.
So to answer your first question, all of them. I would kill everyone they told me to kill because their life comes second to that of my child's.
As to your other question, nothing quite often. I had speeding ticket court the other day. The state trooper who wrote my ticket didn't make it to court. A couple of people who had tickets from the same trooper hired an attorney, and the attorney got the ticket dismissed because of the troopers absence.
When it was my turn I requested that the judge dismissed the ticket because of the troopers absence.
He said we could just reschedule for a time when the trooper was present.
I demanded a trial that day, right now.
I could tell he was somewhat upset but he dismissed my ticket.
I've refused to give ID to cops before while being a pedestrian. They asked more firmly a second time, which I more politely refused.
So the answer is, when you tell law enforcement no in America, they bluff you a little first, to try to get you on the second go, then they follow the law. Just be sure it's on your side when you say no.